Open a web browser and go to `http://10.0.0.1`
Log in with your Comcast/Xfinity admin username and password
Select `Gateway`
Select `Connection`
Select `WiFi`
Choose the WiFi network you want to change
Enter a new WiFi password in the password field
Save or apply the changes
Reconnect your devices using the new password
If you use the Xfinity app, open the app
Select `WiFi`
Select `WiFi settings`
Select `Edit WiFi`
Change the password
Save the changes